Without limiting the scope of the present invention, its background is described with reference to optimizing the production of hydrocarbons from a well that uses gas injection to artificially lift the fluid contained in the wellbore.
It is well known in the subterranean well operation arts that the natural pressure of the formation in which the well is completed may be or may become insufficient to produce fluids out of the wellbore, such that the fluids do not flow to the surface at an optimal volume flow rate or do not flow at all. In order to restore production to the optimal volume flow rate, therefore, an artificial method of producing the fluids through the wellbore must be implemented.
A common method used to increase or restore production to a well is a gas-lift system, whereby some of the gas produced from one or more wells is injected back into the production tubing of the well at one or more downhole locations. This effectively reduces the density of the fluid column in the wellbore, allowing the reservoir pressure to lift the fluid out of the wellbore.
In typical gas-lift wells, fluids produced from the production wellbore are routed into a separator tank on the surface. The separator may be fed by one or more production wells. Once separated from the water, oil, and other fluids produced from the reservoir, the gas is usually then routed to a compressor to increase its pressure. After the compression stage, the gas may be sent to a sales line, a gas-injection line, or both. Gas that is routed into the gas-injection line is injected into the fluid column in the production tubing of the wellbore of the gas-lift well. This is usually accomplished by installing gas-lift valves on the production tubing that allow the injection gas to be forced into the annulus and pass into the production tubing and the fluid column contained therein.
To maximize fluid production from a gas-lift well, the volume flow rate of the injection gas must be maintained at an optimum level. In typical gas lift systems, however, some gas is sent to the sales line even if the optimum volume flow rate of injection gas has not been reached. Thus, the well may produce below the optimum level for an extended time. Further, because both sales gas and injection gas are compressed, the power requirements of the compressor fluctuate with fluctuations in the volume flow rate of gas produced by the well.
It is an object of the present invention, therefore, to prioritize maintaining the optimum level of gas production using the gas-lift process over sending gas into the sales line when the well is not producing gas at the optimum rate due to decreases in formation pressure.